Medical research has applied advanced temperature measurement techniques such as infrared thermography and liquid crystal films to diagnose and identify various forms of vascular diseases and tumors. Since temperature is an indicator of circulatory function, techniques have been developed to measure the effects of nerve blocking drugs on the circulatory system by measuring temperature. In addition to diagnostic applications, temperature measuring devices have been used in medicine to locate everything from veins to placental attachment sites.
A recent invention using liquid crystals (U.S. Pat. No. 4,378,808) can be used to detect unwanted infusion of fluids into tissue when an IV fails. U.S. Pat. No. 4,064,872 discloses a device for measuring temperature differentials on skin surfaces comprising dots of liquid crystals sealed between thin films. U.S. Pat. No. 3,951,133 discloses two or more sheets of liquid crystal thermal films assembled side by side where each sheet changes color at a different temperature. U.S. Pat. No. 4,154,106 discloses a disposable temperature indicator with an array of dots of crystals sensitive to respectively different temperature ranges.
Temperature measurement has also been used for therapeutic purposes in the field of biofeedback. A variable signal tone, light or meter provides the patient with a feedback signal that relates to the patient's skin temperature. The patient is trained to respond to this type of feedback by modifying his temperature and/or behavior.
Liquid crystal technology has been used for numerous applications where temperature mapping is required. For example, a thin uniform coating of liquid crystals may be applied to the surface of an object to be evaluated or to a film that is coated with the liquid crystal material and then placed on the surface of an object (animate or inanimate). Liquid crystal material can be conventionally formulated to respond to either a wide temperature range or a narrow temperature range. Individually, each formulation has disadvantages. In the case of wide temperature range formulations, much valuable detail information may be lost due to lack of temperature resolution. Narrow temperature range formulations, on the other hand, offer detailed temperature resolution--but inherently can not accommodate large variations in temperature. Various systems have been devised that utilize masks to reveal numbers or symbols when liquid crystals reflect light thus allowing a number of narrow temperature range formulations to be stacked or used side by side. Although these compound systems offer more information than single formulations, they have not been very useful for mapping small details and patterns.